The present invention concerns a process for the production of a pharmaceutical agent for oral or topical administration in the treatment of protozoal diseases, in particular of leishmaniasis.
Leishmaniasis is a name for various tropical diseases which are caused by flagellates of the genus Leishmania and is transmitted by various blood-sucking insects. The manifestations of leishmaniasis may be visceral (kala-azar), mucocutaneous (american leishmaniasis) or cutaneous (Aleppo boil or diffuse cutaneous leishmaniasis). The incubation period is weeks or months. A very high mortality rate is observed in untreated cases, in particular with kala-azar and american leishmaniasis.
The therapeutic agents used today for the treatment of leishmaniasis are pentavalent antimony compounds (e.g. sodium stibogluconate) and aromatic diamidines. A disadvantage of these drugs is, however, that they cause severe side-effects such as nausea and vomitting due to their high toxicity. Moreover there are already Leishmania strains which are resistant to antimony.
Croft et al (Biochem. Pharmacol. 36 (1987), p. 2633-2636) describe experiments in which the effectiveness of alkyl phosphocholines against Leishmania donovani was investigated. The effect of alkyl phosphocholines was tested in comparison with the effect of the standard therapeutic preparation, sodium stibogluconate, (Pentostam) when administered subcutaneously. In this process it was found that alkyl phosphocholines, in particular C22 alkyl phosphocholines are active against Leishmania. It was, however, also established that the alkyl phosphocholines, in particular hexadecyl-phosphocholine, were highly toxic for the experimental animals, in particular for macrophages in therapeutically effective doses so that they do not represent a real alternative when administered subcutaneously to the known therapy with sodium stibogluconate.
Thus the object of the present invention was to provide a pharmaceutical agent for protozoal diseases, in particular for leishmaniasis, in which the disadvantages of the state of the art, in particular with regard to the severe side-effects, are at least partially eliminated.
The object according to the present invention is achieved by a process for the production of a pharmaceutical agent for oral or topical administration in the treatment of protozoal diseases, in particular of leishmaniasis, which contains as the active substance one or several compounds having the general formula I 
in which R1 is a saturated or monounsaturated or polyunsaturated hydrocarbon residue with 12 to 20 C atoms and R2, R3 and R4 denote independently of one another hydrogen, a C1-C5 alkyl group, a C3-C6 cycloalkyl group or a C1-C5 hydroxyalkyl group whereby two of the residues R2, R3 and R4 can together form a C2-C5 alkylene group which, if desired, can be substituted with an xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 or NR5 group, in which R5 is hydrogen, a C1-C5 alkyl group, a C3-C6 cycloalkyl group or a C1-C5 hydroxyalkyl group as well as, if desired the usual pharmaceutical auxiliary, diluting, carrier or/and filling substances.
In the general formula I, R1 can be branched or straight-chained. R1 is preferably a straight-chained hydrocarbon residue with 16 to 20 C atoms, in particular a hexadecyl, octadecyl, oleyl, elaidyl, eicosyl or eicosenyl-cis-(xcfx89-9) residue. R1 is particularly preferably a hexadecyl or octadecyl residue.
Examples of suitable residues R2, R3 and R4 in the formula I are for instance methyl, ethyl, propyl, butyl and pentyl residues, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl residues, hydroxymethyl, hydroxyethyl and hydroxypropyl residues. Two of the residues R2, R3 and R4 can for example form a pyrrolidine, a piperidine or a morpholine group. At least one of the residues R2, R3 and R4 is preferably different from hydrogen, it is particularly preferred that all 3 residues are different from hydrogen.
Examples of preferred residues R2, R3 and R4 are methyl, ethyl, hydroxyethyl and C3-C6 cycloalkyl residues. If one of R2, R3 and R4 is a cycloalkyl residue, then the other two residues are preferably methyl residues. It is particularly preferred that the residues R2, R3 and R4 are independently of each other methyl or ethyl residues. It is most preferred when R2, R3 and R4 are methyl residues so that alkyl phosphocholines represent a particularly preferred class of compounds which is suitable for the production of an agent against protozoal diseases, in particular against leishmaniasis.
It was surprisingly found that compounds having the general formula I when administered orally or topically show no measurable side-effects and a very much higher activity than sodium stibogluconate. In any case the therapeutic agents according to the present invention constitute the first forms of oral therapy for leishmaniasis diseases, and they are considerably more effective than Pentostam, a standard therapeutic preparation used worldwide in the liver and in particular also in the spleen.
In a preferred embodiment of the present invention the oral or topical therapeutic preparation additionally contains one or several alkyl glycerols having the general formula II 
in which one of the residues R6 and R7 denotes an alkyl group with 2 to 12 C atoms and the other residue denotes a hydrogen atom. An alkyl glycerol mixture is preferably used which contains nonyl or octyl glycerol, hexyl or pentyl glycerol and propyl or ethyl glycerol as well as, if desired, water.
The pharmaceutical agent according to the present invention contains in one dosage unit preferably 5 to 2000 mg, particularly preferably 10 to 500 mg of one or several compounds having the general formula I. For topical administration the pharmaceutical agent according to the present invention preferably contains 5 to 200 mg of one or several compounds having the general formula I per ml of an alkyl glycerol having the formula II or of a corresponding alkyl glycerol mixture.
For oral administration the pharmaceutical agent according to the present invention is preferably formulated as a drinking solution with a daily dosage between 1 and 10 mg/kg of one or several compounds having the general formula I.
The production of an oral pharmaceutical agent according to the present invention can on the other hand also be carried out by mixing or homogenizing one or several compounds having the general formula I with the usual physiologically tolerated filling, carrier, dilution or/and auxiliary substances at temperatures between 20 and 120xc2x0 C. and, if desired in order to prepare formulations which contain 10 to 800 mg of compounds having the general formula I in one dosage unit, the mixture thus obtained is poured into hollow cells of an appropriate size or filled into capsules of an appropriate size or granulated and then pressed into tablets, if desired, with addition of further common auxiliary substances. The active substance can for example be mixed with one or several of the following auxiliary substances: starch, cellulose, lactose, formalin-casein, modified starch, magnesium stearate, calcium hydrogenphosphate, highly-dispersed silicic acid, talcum and phenoxyethanol. The mixture obtained is granulated, if desired, with an aqueous solution containing for example gelatin, starch, polyvinyl pyrrolidone, vinylpyrrolidon-vinyl acetate copolymerisate or/and polyoxyethylene sobitanmonooleate, as constituent and the granulate is homogenized, if desired, with one or several of the aforementioned auxiliary substances. Subsequently this mixture can be pressed into tablets or filled into capsules whereby the tablets or capsules each contain 10 to 800 mg of active substance in one dosage unit.
In a particularly preferred embodiment the active substance is suspended with soybean lecithin as well as, if desired, 0.1 to 0.5 parts by weight phenoxyethanol (in relation to one part by weight of the active substance) at temperatures between 33 and 37xc2x0 C. in melted resin fat and homogenized and subsequently the mixture is poured into hollow cells whereby one dosage unit contains 10 to 800 mg of the active substance.
Moreover the active substance can be homogenized at a temperature between 50 and 120xc2x0 C., if desired in the presence of one or several emulsifiers or/and 0.1-0.5 parts by weight phenoxyethanol (in relation to 1 part by weight of the active substance) with at least one of the following substances: paraffin, vaseline, aliphatic alcohol with 12 to 25 C atoms, sorbitanmonopalmitate, aliphatic monocarboxylic acid with 15 to 20 C atoms, polyoxyethylenepolyol fatty acid ester. If desired, the mixture obtained can be emulsified with addition of a multivalent lower (preferably C2-C3) aliphatic alcohol (e.g. ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and in particular glycerol).
On the other hand, if desired, the active substance can be dissolved at temperatures between 30 and 100xc2x0 C. in the presence of 0.1-0.5 parts by weight phenoxyethanol (in relation to one part by weight of the active substance) as well as, if desired, in the presence of an emulsifier and if desired the solution thus obtained is filled up with sufficient water or vegetable oil so that the final solution contains 0.1 to 5 % by weight of the active substance.
The active substance can also be mixed together with an alkyl glycerol having the general formula II or with a mixture of such alkyl glycerols as well as, if desired, water in which 1 to 30 parts by weight alkyl glycerol having the general formula II or of a corresponding alkyl mixture and if desired 1 to 30 parts by weight water, each in relation to 1 part by weight active substance according to general formula I, are used.
The present invention also concerns the use of one or several compounds having the general formula I as the active substance for an oral or a topical agent for treating protozoal diseases, in particular leishmaniasis. In this connection the agent can additionally contain one or several alkyl glycerols having the general formula II, in particular for topical applications.
Finally the invention also concerns a process for the treatment of protozoal diseases, in particular of leishmaniasis, which is characterized in that a pharmaceutical agent produced according to the present invention is administered topically or orally.
The production of compounds having the general formula I is described in detail in the examples for hexadecyl-phosphocholine. Further methods for the production of compounds having the general formula I are described for example in DE-A 27 52 125, DE-A 36 41 379, DE-A 36 41 491, DE-A 40 13 632, DE-A 36 41 377, the literature cited in these or in earlier patent applications or patent specifications of the same applicant. Reference is expressly made to this literature for the present patent application.
The pharmaceutical agents according to the present invention are preferably used for the treatment of leishmaniasis. Other protozoal diseases which can be treated by the agent according to the present invention are for instance malaria, trypanosomiasis, toxoplasmosis, babesiosis, amoebic dysentery and lambliasis. The agents according to the present invention are in particular suitable for those diseases in which the pathogen is present in organs such as the liver, spleen or kidney.
It is intended to elucidate the invention further by the following examples.